MUZISHARE X7 Tube Amplifier Double High Pressure Rectifier Power Amplifier Ultra-linear/ Triode Mode. Specification: Rated output power: 25W + 25W (RMS triode mode), 45W + 45W (RMS ultra-linear mode) Harmonic distortion: 1% (1kHz) Frequency response: 15Hz30kHz (-1.5dB) Input sensitivity: 280mV; 520mV(pre in) Input impedance: 100K? Output Impedance: 4? 8? SNR: 92dB Output balance of the left and right. Usually it cost about 35USD-50USD. Thanks for your understanding. If you receive defective item, please kindly notify us within 14 days.